The Hungry Hollow Formation on the southeastern margin of the Michigan Basin is interpreted as a composite stratigraphic unit representing the lateral equivalents of two depositional cycles in the northern Appalachian Basin. The basal beds (? = Pompey and upper Levanna transgressive hemicycle of the upper Skaneateles Formation in New York) are separated by disconformity surfaces both from the underlying Arkona Shale and from the upper part of the Hungry Hollow (= upper part of Centerfield Limestone Member). These basal beds were deposited on eroded, overcompacted claystones of the Arkona Shale, contain a diverse suite of remanie sediments, and fill deep, delicately sculpted furrows of Cruziana transversa n. ichnosp., C. reticulata n. ichnosp., and Rusophycus bilobatum (Vanuxem, 1842). This lower disconformity may be recognizable regionally over the Northern Midcontinent. Overlying beds feature the lowest local occurrence of an offshore-aspect conodont fauna of the lower Polygnathus varcus Subzone. The underlying Arkona Shale yields Icriodus-dominated (nearer-shore aspect) faunas apparently representing Polygnathus xylus ensensis Zone assemblages. The upper part of the Hungry Hollow Formation and overlying lower part of the Widder Formation represent an offlap-onlap cycle within the lower Polygnathus varcus Subzone that is comparable to that of the upper part of the Centerfield Limestone.

Cruziana and Rusophycus from the Hungry Hollow were not originally produced as “under-tracks” but were formed at the sediment–water interface on erosion-resistant, overconsolidated muds. The producer of Cruziana reticulata n. ichnosp. appeared in the benthic community of the field area before the excavator of C. transversa n. ichnosp. and of Rusophycus bilobatum (possibly the trilobite Dipleura). The degree of limb swing required to produce the reticulate scratch patterns in C. reticulata n. ichnosp. suggests the evolution of specialized coxa-sternite and inter-podomere hinges that were not previously considered to be present in trilobites. Comparable reticulate scratch patterns occur as early as the earliest Cambrian and are apparently related to excavation on disconformity-related mud firmgrounds.

A trace-fossil assemblage is exposed in the uppermost portion of an interpreted tidal sand-flat deposit in the Upper Mississippian Tar Springs Sandstone in southwestern Illinois. Sedimentary structures, indicative of a tidal origin for this unit, include herringbone crossbeds, flaser and lenticular beds, reactivation surfaces, small channel scours, and shrinkage cracks. The trace fossils include trackways, trails, feeding structures, dwelling burrows, and escape structures. Vertical dwelling and escape structures dominate the assemblage with lesser numbers of horizontal and inclined traces. The ichnological and sedimentological characteristics are diagnostic of the Skolithos ichnofacies. Preservation of the assemblage at the top of the Tar Springs Sandstone was the result of substrate stabilization as the tidal flat subsided and was transgressed. The present trace-fossil assemblage probably was formed by a combination of a pre-omission tidal-flat suite and an omission suite formed during and after the transgression. Preservation of the assemblage suggests a passive transgression with minimal scouring and reworking of the tidal-flat deposit.

The Treptoceras duseri shale unit within the Waynesville Formation of Late Ordovician (early Richmondian) age in southwest Ohio and the equivalent Trilobite shale unit in the same formation exposed in adjacent portions of Indiana represent an Ordovician shallow marine mud-bottom epeiric sea facies. These fine-grained elastics contain a moderately diverse mollusk-trilobite assemblage dominated by vagrant epifaunal detritus-feeding calymenid and asaphid trilobites, large endobyssate and infaunal filter-feeding pelecypods, and nektonic nautiloids. Articulate brachiopods, ectoprocts, and pelmatozoan echinoderms form only minor elements of this fauna.

This mollusk-trilobite assemblage was common in Late Ordovician shallow marine clastic environments where mobility was an asset and there was an abundance of oxygen and food resources. Such assemblages are characteristic of the Lorraine Fauna of Late Ordovician (Edenian to Richmondian) age that occurs from the Ohio Valley north and east into New York, Ontario, Quebec, and Ireland. These early Paleozoic mud-bottom assemblages were considerably modified by the Late Ordovician extinction event and were replaced in the Silurian and Devonian by distinctly different assemblages dominated by large epifaunal strophomenid and spiriferid brachiopods, crinoids, and phacopid trilobites.

A large collection of Silurian Syringoporidae, mainly from the Limestone Point and La Vieille formations of northern New Brunswick, includes one new species and three species previously described from this area. Syringopora lambei n. sp. is distinguished from the superficially similar S. bifurcata Lonsdale by its larger corallites with much broader axial tubes and less frequent corallite contacts. Similar problems which have existed in the past in the distinction of S. compacta Billings and S. reteformis Billings can be resolved, as shown in this study, on the basis of the larger, geniculate and densely-packed corallites of S. reteformis. All four species are defined using more quantitative data than has previously been applied to syringoporid taxonomy. A new lectotype for S. compacta is proposed. Recognition of epibionts on a corallum of S. bifurcata as virtually identical to the “epithecal scales” used to distinguish Syringoalcyon Termier and Termier from Syringopora Goldfuss argues strongly against the continued recognition of the former as a separate genus. Preliminary analysis of syringoporid distributions in relation to stratigraphy and sedimentary associations suggests strong facies and paleoenvironmental control on these distributions. For this reason and because of their long stratigraphic ranges, no well-defined biozonal scheme can be proposed at this time.

Rousseauspira teicherti, a new genus and species of an unusual, untwisted, horn-shaped gastropod operculum from shallow-subtidal limestones of the Upper Ordovician of Alaska and the Middle Ordovician of California, is described and compared to two other Ordovician opercula, Ceratopea Ulrich, 1911, and Teiichispira Yochelson and Jones, 1968. The shell to which the operculum belonged is not yet known.

Analyses of shell shape variation in epifaunal and semi-infaunal myalinids from the LaSalle “cyclothem” attest to the extensive shape plasticity of some Late Pennsylvanian myalinids. Mean shell shapes differ significantly within and among species across three nearshore facies. Discriminant analyses of Fourier biometric data categorized by taxonomic, populational (habitat), life-mode, and “multi-species habitat assemblage”” discriminant groups reveal patterns of shape change and variation across an inferred environmental stress gradient in addition to taxonomic and life-mode shape differences. Fourier harmonic data are good indicators of shape differences between epifaunal and semi-infaunal life modes. Mean shapes of epifaunal species vary among habitats. Within-habitat shell shape convergence occurred between Myalina glossoidea and M. (Orthomyalina) slocomi. Interpopulational shape divergence occurred among all populations of M. (Orthomyalina) slocomi, M. glossoidea, and M. wyomingensis. Within-species variation among habitats produced significant mean shape differences among each of three “multi-species habitat assemblages.” Results indicate that a portion of the variation is of ecophenotypic origin.

Mean interspecific shape differences reflect internal functional organization and life modes. Intraspecific shape differences among epifaunal species could reflect physical and biotic habitat variables. Several harmonic amplitudes vary in concert with inferred environmental variation among habitats. Although biologic interpretation of harmonic data is problematic, parallel trends in fifth harmonic amplitudes of epifaunal species mirror inferred differences in water turbulence among habitats and could reflect shape variation related to byssal attachment.

Stress gradient trends in intraspecific shape variability cannot be collectively explained by either of the antithetical stability-diversity-variation hypotheses. Each species exhibits a different nonmonotonic trend. Maximal levels of intraspecific variation within each species occurred within different habitats. Within-species differences in levels of variation could result from genetic variation among populations as well as ecophenotypic influences. Comparative studies of ontogenetic shape change between valves of individuals, among individuals, and among populations are necessary to determine the relative influence of environmental variables on shape variation and evolutionary significance of phenotypic plasticity.

A Recent sinusoidal trail made by a biting midge (family Ceratopogonidae, genus ?Bezzia) moving on the surface of wet mud along the edge of a freshwater pond has been observed. The trail is similar to the trace fossil Cochlichnus Hitchcock, 1858. The wave length, wave amplitude, and overall form and shape of this modern trail compares favorably to Eocene wave-like trails attributed to nematodes. Consequently, a ceratopogonid larva is believed responsible for at least some of those fossil trails.

Burrows of the thalassinidean shrimp Callianassa californiensis and Upogebia pugettensis, which resemble the trace fossils Thalassinoides and Ophiomorpha, respectively, occur on the southern tidal flats at the western front of the Fraser Delta. Burrow densities for both shrimp species are highest at lower intertidal levels immediately inshore of an extensive bed of Zostera marina eelgrass, but the high-density shrimp populations are segregated: the highest densities of C. californiensis burrows (350–450 burrow openings/m2) occur in a strip of clean sandy sediments, whereas U. pugettensis burrows are most abundant (30–80 burrow openings/m2) in a patch of muddy sands and sandy muds. On the tidal flats of the Fraser Delta as a whole, however, textural properties of the sediment show no consistent correlation with the burrow density of either shrimp.

In the eelgrass bed, eelgrass root mats appear to markedly restrict the density of C. californiensis burrows. Towards the shore, the well-lined dwelling burrows of U. pugettensis occur no higher than mean sea level where maximum continuous exposure is ≤0.5 days. In contrast, C. californiensis, which has an unlined feeding burrow and a higher tolerance for anoxia, is present up to the margin of the local salt marsh which lies near the mean higher high water level where the flats can be exposed continuously up to 5 days.

In situ experiments indicate that C. californiensis extrudes 18 ± 9 ml of wet sediment/shrimp/ day onto the substrate surface, while U. pugettensis seldom forms a mound around its burrow entrance. Burial of filter-feeding postlarval U. pugettensis under the mounds produced by C. californiensis may increase postlarval mortality and reduce adult populations of U. pugettensis in areas of high C. californiensis burrow density.

The results of this study suggest that in distinguishing Ophiomorpha from Thalassinoides more emphasis should be placed on the presence of an extensive burrow lining in Ophiomorpha than on the presence of a knobby burrow exterior, because the former characteristic has a more profound bearing on burrow function, physiology of the occupant organism, and, consequently, burrow distribution.

A diverse cirriped fauna, including the scalpelloids Cretiscalpellum homseyi n. sp., Arcoscalpellum withersi Collins, Arcoscalpellum bakeri Collins, Virgiscalpellum gabbi heintzi n. subsp., Virgiscalpellum sp., V. cf. V. gabbi apertus Collins, and the brachylepadomorph Brachylepas solida n. sp., occurs in the Upper Cretaceous Mt. Laurel Sand at the Biggs Farm locality on the Chesapeake and Delaware Canal, New Castle County, Delaware. This fauna represents the Maastrichtian Virgiscalpellum Zone originally identified in the Ripley and Prairie Bluff formations of the eastern Gulf Coast.

Lower Carboniferous (Viséan-?early Namurian) conodonts, and some of their variably complete reconstructed apparatuses, are described from cyclic marine carbonates, associated with evaporites and mud rocks, of the Windsor Group, Magdalen Islands, Quebec, Canada. The conodont fauna includes Clydagnathus windsorensis, Cavusgnathus unicornis, Taphrognathus transatlanticus, Hindeodus cristula, Hindeodus? scitulus, Vogelgnathus campbelli, Ozarkodina laevipostica, Mestognathus bipluti, Mestognathus spp., Spathognathodus? n. sp. A, and Apatognathus spp.

A fauna of disarticulated Devonian fossil fish remains includes osteolepid, palaeoniscoid, acanthodian, placoderm, and possible agnathan material. Lithologic and biostratigraphic evidence for a lacustrine or paludal environmental interpretation is examined. Palynomorphs from the deposit suggest a Middle (Givetian) to early Late (Frasnian) Devonian age which is compatible with the faunal evidence.

A single phyllodont tooth plate was identified in core from the Permian San Andres Formation of the Palo Duro Basin, Texas Panhandle. This is the first vertebrate fossil recorded from the San Andres Formation, and extends the Permian range of phyllodont dentitions into the lower Guadalupian Stage. The life environment is inferred to have been normal marine to marginally hypersaline, based on the occurrence of the specimen near the top of a carbonate unit in a carbonate-evaporite cycle.

An extinct ictalurid catfish, Ictalurus spodius n. sp., is described from the Pleistocene of Central Mexico. It shares derived osteological characters with the subgenus Ictalurus and the I. punctatus species group. The new species is known from middle Pleistocene fluvial and lacustrine sediments and was abundant until near the end of the Pleistocene when it was replaced by a closely related species, I. dugesi. The latter is known from late and post-Pleistocene lake-bottom deposits and is widespread in Central Mexico today.

Four species of rhinoceros occur together in the Barstovian (middle Miocene) faunas of southeast Texas, a unique situation in the Miocene of North America. Two are assigned to normal contemporary High Plains species of Aphelops and Teleoceras, and two to dwarf species of Peraceras and Teleoceras. The dwarf Peraceras is a new species, P. hessei. The dwarf Teleoceras is assigned to Leidy's (1865) species “Rhinoceros” meridianus, previously referred to Aphelops. “Aphelops” profectus is here reassigned to Peraceras.

The late Arikareean (early Miocene) Derrick Farm rhino, erroneously referred to “Caenopus premitis” by Wood and Wood (1937), is here referred to Menoceras arikarense. Menoceras barbouri is reported from the early Hemingfordian (early Miocene) Garvin Gully local fauna of southeast Texas. The rhinos from the early Clarendonian Lapara Creek Fauna are tentatively referred to Teleoceras cf. major.

The three common genera of middle late Miocene rhinoceroses of North America (Aphelops, Peraceras, Teleoceras) are rediagnosed. Aphelops and Peraceras are more closely related to the Eurasian Aceratherium and Chilotherium (all four together forming the Aceratheriinae) than they are to the American Teleoceras. Contrary to Heissig (1973), Teleoceras is more closely related to the living rhinoceroses and their kin (together forming the Rhinocerotini) than it is to the Aceratheriinae.